Flow concentrators made of various hard and/or soft flexible materials have been fastened around the outside of the borehole flowmeters to increase sensitivity to slow flow, especially in larger diameter holes. Various other types of spring loaded expanding funnels have been used which fill the annulus between a flowmeter and the borehole wall. Such a funnel is disclosed in U.S. Pat. No. 4,800,752 to Piers. However, such devices may not adequately seal the hole, especially in holes having large diameter variations or irregularities, since these devices permit an unknown portion of the fluid to bypass the flowmeter. Additionally, there is no disclosure in the Piers patent as to how to adequately fill the tubular ring without over pressuring and bursting the ring, or under pressuring and having inadequate sealing. Further, problems may arise when such devices are used in deep boreholes having high pressures because there is no pressure equalization either between the reservoir liquid and the well fluid or for the electric pump motor. Also, the device disclosed in the Piers patent offers limited adjustability of packer diameter.
Borehole, wall conforming, inflatable packers, which are inflated with fluid pressure from the surface, are commonly used. This type of packer requires one or more pipes, conduits or tubes leading to the surface, and very careful pressure control to assure adequate inflation without over-pressure which would burst the bladder or under-pressure which would not give adequate sealing. This becomes very difficult to accomplish at great depths below the fluid surface or where the borehole fluid level is unknown or is subject to large changes. These conventional surface inflated fluid packer systems are usually heavy and require a drill rig or work-over rig to position or move the packers, especially in deep holes. U.S. Pat. No. 5,094,294 to Bayh, III is an example of a production well pump and packer assembly which is hydraulically set and released from the surface.
U.S. Pat. No. 4,892,144 to Coone and U.S. Pat. No. 5,027,894 to Coone et al. address some of the above-mentioned problems by providing an inflatable wall conforming packer which is reinforced by thin, elongate strips surrounding the packer. These strips are further used to grip the well bore as the packer is expanded in order to maintain the packer in its vertical position. However, these packers are heavy and still must be inflated by fluid pressure supplied from the surface through connecting conduits, pipes or tubing.